The present invention relates to an aiming level device for a motor vehicle headlamp for measuring an amount of deviation of the light beam from the headlight in vertical and horizontal directions from a proper aiming direction. The level device is mounted on a reflector when applied to the headlamp of a movable reflector type, or mounted on the movable unit of lamp body and reflector when applied to the headlamp of a movable unit type.
In a conventional vehicular headlamp of a movable reflector type, as shown in FIG. 1, a reflector 2 on which is mounted a bulb 3 is pivotally supported with respect to a lamp body 1. The amount of deviation of the reflector in the vertical direction is measured with a level device 4 mounted on the reflector 2. As shown in FIGS. 2 and 3, the level device 4 is provided with a casing 5 having an opening directed upward and a lid 6, acting as a bubble vial supporting frame, supporting a bubble vial 7 and assembled on the casing 5. The conventional level device 4 is also provided with a zero-point adjusting screw 8a, a compression coil spring 8b, and concave and convex engaging parts 9a and 9b. The lid 6 is held by the screw 8a and resiliently engaged by the spring 8b. The position of a bubble contained within the bubble vial 7 is adjusted by adjusting an inclination angle of the lid 6 by rotating the screw 8a, whereby the zero-point of the level device can be adjusted. Reference character L (FIG. 1) and reference numeral 2a (FIG. 3) respectively indicate the optical axis of the headlamp and a plate-like extending part of the reflector 2 for mounting thereon the level device.
According to the conventional level device 4, however, since the lid 6 is supported by the zero-point adjusting screws at a side end part of the pivot point and the other end part, the total length of the level device is unavoidably long and therefore causes the following difficulties.
First, as shown in FIG. 3, since the level device 4, which is generally mounted on an upper wall of the reflector, is elongated in the longitudinal direction, the rear end portion of the level device protrudes a significant amount rearward from the reflector 2. Accordingly, the lamp body 1 in the case of a headlamp of the movable reflector type must have a great depth. Further, in case of a headlamp of the movable unit type, the headlamp unit must be spaced apart from the lamp housing. In either case, the headlamp must be large in size. In other words, the conventional level device cannot be applied to a compact headlamp, especially one having a small depth.
Second, generally the level device 4 is mounted on the reflector 2 inside the lamp body 1 in the case of a headlamp of the movable reflector type, an opening part 1a is formed on a lamp body 1 at a position corresponding to the level device 4, and a transparent removable viewing window 1b is fitted on the opening part 1a for reading a gauge of the level device 4. The zero-point of the bubble vial is adjusted by a screwdriver inserted through the opening 1a after removing the viewing window 1b. However, the viewing window 1b must be large both for purposes of reading the gauge of the bubble vial and for allowing the screwdriver to be inserted through the opening 1a. Accordingly, it is difficult to shape the opening part 1a and the viewing window 1b and, further, light may undesirably leak through the window 1b.
Further, since the conventional level device 4 is constituted by the casing 5, bubble vial 7, lid 6 for holding the bubble vial 7, zero-point adjusting screw 8a and compression coil spring 8b, the number of components is large, which makes the manufacturing cost high.
Furthermore, to assemble the conventional level device 4, since the bubble vial 7 is supported on the rear side of the lid 6, first the bubble vial 7 must be fitted on the arms 6a of the lid 6, and then the lid 6 carrying the bubble vial 7 is mounted on the casing 5. Accordingly, the required assembly steps are quite intricate.